Different routes of co-administration of magnesium sulphate with spinal anesthesia in knee arthroscopy: Randomized controlled trial

Background
Adequate pain management has a great importance for smooth postoperative recovery, early hospital discharge and early rehabilitation. In this study is we compare between the analgesic effect and possible side effects of different routs of magnesium sulphate administration in cases of spinal anesthesia for knee arthroscopy.
Methods
120 patients scheduled for knee arthroscopy 4 groups (30 patients each): received only Bupivacaine intrathecally. received 50 mg Mg sulphate with Bupivacaine intrathecally, 10 min after intrathecal injection, received intravenous injection of 30 mg/kg Mg sulphate in 100 ml saline over 10 min followed by 10 mg/kg intravenous infusion over one hour and received intra-articular injection of 800 mg Mg sulphate diluted in 12 ml normal saline (0.9% NaCl) 10 min before the end of surgery. Operative time in minutes, VAS at rest and at passive movement, time to be able to perform knee flexion, time from end of surgery until first requirement of analgesics, analgesic consumption, hemodynamic changes and any possible side effects were recorded.
Results
Regarding Time to be able to perform knee flexion, time taken from end of surgery until first analgesic dose and amount of pethidine consumption in first postoperative 24 h, group Mg-Art is significantly better than other groups (P = 0.000) (P = 0.000) (P = 0.000) respectivly. Group Mg-Iv is significantly better than group Mg-Sp and group C as regards time taken from end of surgery until first analgesic dose (P = 0.000) and as regards amount of pethidine consumption in first postoperative 24 h (P = 0.000). VAS at rest and with passive movement in group Mg-Art is significantly lower other groups (P = 0.000).
Conclusion
Intraarticular administration of magnesium sulphate is found to be better than Intravenous magnesium and intrathecal in postoperative analgesia.